Access to gem-Diindolylcyclopropanes via Double Indolylation of gem-Difluorocyclopropanes

gem-Difluorocyclopropanes (gem-DFCPs) have gained significant attention as versatile fluorinated synthons in organic synthesis due to their unique structural and electronic properties. Recent advancements have demonstrated the utility of gem-DFCPs in transition-metal-catalyzed cross-coupling reactions with indoles, enabling the synthesis of monofluoroallylic indole derivatives. In this study, a transition-metal-free double indolylation of gem-DFCPs was developed, preserving the cyclopropane core and facilitating the direct incorporation of two indole units. This method, optimized under mild conditions using NaOtBu and DMSO, provides access to gem-diindolylcyclopropanes with high yields and broad substrate scope. Mechanistic studies, including deuterium-labeling experiments, suggest a base-mediated elimination and nucleophilic addition pathway. The scalability and postfunctionalization potential of the products highlight the synthetic utility of this transformation, particularly in the late-stage modification of bioactive molecules. This research expands the synthetic toolbox for constructing densely functionalized cyclopropane architectures with potential pharmaceutical relevance.